1. Field of the Invention
This invention relates in general to an image correction method, and more particularly, to an image correction method to help avoid error images.
2. Description of the Related Art
In terms of functionalities, the scanner is an intermediate between the photocopier and the camera. In the past, the application of scanners is restricted to special art work due to the very high cost. In recent years, the rapidly growing computer technique and the active competition in the market result in signification cost reduction for the scanners. Eventually, the scanner has become a popular peripheral of personal computers.
Depending on the price or functionality, scanners can be categorized into several types. Typically scanners can be categorized into handheld scanner, sheet-feed scanner, card reader, film scanner and flatbed scanner. The flatbed scanner includes a glass flatbed on which the document to be scanned is disposed. By shifting the sensor, the information of the document is read. As the structure is not very complex, and the method for using it is not difficult, plus the outstanding function expandability, the flatbed scanners have become the application mainstream for the current computers.
Basically, scanners are divided into black-and-white type and color type with respect to color display, and reflective type and transparent type with respect to the scanning method. The following uses a reflective type color scanner as an example to introduce the basic structure of a scanner. Referring to FIG. 1, the basic structure of a color scanner 10 is shown. The color scanner 10 comprises a lamp 102, an optical system 104, a charge-coupled device (CCD) 106, and an analog/digital (A/D) converter 108. Functions of various parts of the color scanner 10 are further described as follows.
When the lamp 102 is used as the light source of the color scanner 10, the light generated by the lamp 102 is incident on the document 110. The light is then reflected by the document 110 to project onto the optical system 104. The lamp 102 can be a fluorescent lamp, a cold cathode ray tube, or a light emitting diode array.
The optical system 104 consists of a reflection mirror 112 and a lens 114. Being focused by the reflection mirror 112 and the lens 114, the light reflected by the document 110 is reflected by the reflection mirror 112, focused by the lens 114, and then incident on the charge-coupled device 106.
The function of the charge-coupled device 106 includes converting the detected light intensity into photocurrent, which is then stored in the storage electrodes and converted into signal charges to generate various potential.
The analog/digital converter 108 converts the analog signal of the charge-coupled device 106 into a digital signal, and transmits the digital signal into a computer 118.
When the scanner is scanning a document or a picture, the non-uniformity of the lamp requires an image compensation operation. Generally speaking, a correction document is used for image correction. For example, for the reflective type scanning, a black correction document and a white correction document are used for image correction. If the correction document contains any unwanted object thereon, the unwanted streaking (LBB) effect is generated in the scanned image. Currently, there is no image correction method able to avoid such LBB effect.